Thinking is an encapsulated concept. The process thus far involves mechanisms beyond what the current levels of science and technology can investigate, and thus the mystery of the unknown provides enough ambiguity to associate with a free mind or an unbound noumenon. What would be of more interest to concern oneself about is whether one would still consider oneself as a free-thinking being or having such type of mind once made aware of what exactly makes the mind tick.
Nonetheless, the ambiguity of what thought is can never be resolved simply by observing the limited expressions seeping through to the environment; a purely mechanical observation sees not of the whole. Consider the mind; it is a closed entity in itself whose sole interactive methodology is through the shell (the body, in its mechanical nature). Observing the shell cannot fully disclose the workings of the mind, the manifestation of something out of the shell. The mental entity functions as an isolated and unobservable set of processes.
That being said, the boundary of what makes up a mind and what makes up the shell is not concrete. If a body of such functionality can be created for a machine, then the mind in itself, despite the pure mechanisms and software in place of flesh and blood would still be unobservable if manifested. So, what makes humans unique?